1. Field of the Invention
The present invention concerns a cooling device for the movable blade shroud of a turbojet engine turbine.
2. Description of the Prior Art
The continuous research involved in improvement of turbojet engines is aimed primarily at increasing performance while observing the many restrictions imposed by both the possibilities of industrial use and the conditions of equipment use. At the level of the turbines used in these turbojet engines, pursuit of these goals has resulted in the consideration of two conditions: firstly, increasing the operating temperatures and, secondly, reducing or preventing losses affecting the main gas circulation jet.
Various improvements related to this research have been applied and described. In particular, increasingly high temperatures have made it necessary to cool the hot turbine parts, either as a result of operational needs related to problems of expansion aimed at reducing the interaction of operations, or aimed at obtaining desirable wear of the parts in service by reducing the heat gradients and respecting the limits of heat resistance.
For example, U.S. Pat. No. 3,034,298 describes a turbine cooling system. According to FIG. 5 of this patent, the cooling air from a collector 76 is sent through, firstly, holes 168 in the turbine nozzle 65 and secondly, to the turbine ring 102 which the air flows through to be sent out radially in the main jet. An additional cooling circuit is planned for the radially internal parts.
French Pat. No. 1,548,541 concerns a procedure and device for cooling gas turbines. The system described uses the cooling of a feed wheel disc by a tube of an internal cavity from which the cooling air is sent to the area of the blade roots or a ring or rim surrounding the blade tips.
British Pat. No. 1,519,449 concerns a turbojet engine in which air for cooling the turbine is sent into chambers formed in the turbine ring. This air is sent into the main gas flow via passages through additional blading which sends this air in the direction of the flux obtained at the main guide vane. The release of this air in the jet maintains a centripetal radial component.
These previous arrangements do not provide a satisfactory solution to the problem of cooling movable blade shrouds. Therefore, the objective of the present invention is to define a cooling device for the peripheral collars of movable blades of a turbine in which, by state of the art techniques, an external chamber with an air supply provides the cooling air to stationary vanes of a distributor located above the movable blades by passing through a portion located above the blades and to a turbine ring which constitutes the stationary part opposite the turbine rotor. This device according to the invention is characterized by passages which are also located in the chamber to direct the air toward the peripheral collars of the movable blades of the turbine rotor so as to ensure the cooling of these blade collars from their leading edge on the upper side in relation to the direction of gas circulation in the main gas jet.